Embodiments of the inventive concept are drawn to an image sensor and to a pixel of the image sensor. More particularly, embodiments of the inventive concept are drawn to complementary metal oxide semiconductor (CMOS) images sensors and pixels of CMOS image sensors.
Digital images may be produced using complementary metal oxide semiconductor (CMOS) image sensors or charge coupled device (CCD) image sensors. Complementary metal oxide semiconductor (CMOS) image sensors are solid state image sensing devices that use a combination of p-type and n-type metal oxide semiconductor field effect transistors. Charge coupled device (CCD) image sensors include a high-voltage analog circuit. CMOS image sensors have lower manufacturing costs and are smaller than CCD image sensors and thus are advantageous in terms of power consumption, i.e., consume less power in general than CCD images sensors. In addition, CMOS image sensors offer far greater performance than they did during their early stages of development. Therefore, CMOS image sensors are the preferred choice for use in various electronic products that produce digital images including portable devices such as smart phones and digital cameras.
A pixel array of a CMOS image sensor includes a photoelectric conversion element in each pixel. The photoelectric conversion element generates an electrical signal varying with the quantity of incident light and the CMOS image sensor processes electrical signals to synthesize an image. There is on ongoing demand for electronic products that are more compact and yet which can produce high-resolution images. To meet this demand, the pixels of a CMOS image sensor must be miniaturized.
A trench isolation process, namely, a process which includes the forming of a trench in a substrate, is usually used to isolate elements in a miniaturized pixel. However, a pixel formed using a typical trench isolation process may allow for various types of noise to be produced, due to characteristics imparted to the pixel as a result of the trench isolation process.